Date: 1992-05-12 14:56:41 GMT
Subject: Caloric content of beer (George Fix)
Walter Gude asked in HBD#878 about the determination of calories in
beer. The following empirical formula is remarkably accurate, and
widely used to check direct measurements. Let A, FG, and RE be
defined as follows:
A = alcohol content of finished beer in % by wt.
RE = real extract of finished beer in deg. Plato
FG = final gravity of finished beer.
Then the number of calories per 12 oz. bottle is the following:
(6.9*A + 4.0*(RE - .1))*3.55*FG .
Since A and RE are generally not known to us, additional approximations
are needed. The following are due to Balling, and have proven to be
reasonable. Let OE and be defined as follows:
OE = original extract (i.e., extract of finished wort in deg. Plato)
AE = apparent extract (i.e., measured deg. Plato of finished beer).
RE = .1808*OE + .8192*AE,
A = (OE-RE)/(2.0665-.010665*OE).
To take Walter's specific case, first note that from Plato tables an OG of
1.045 is equivalent to
OE = 11.25 deg. Plato,
while a FG of 1.010 is equivalent to
AE = 2.5 deg. Plato.
RE = .1808*11.25 + .8192*2.5 = 4.08 deg. Plato,
A = (11.25 - 4.08)/(2.0665 - .010665*11.25) = 3.68 % wt.
We conclude that there are
( 6.9*3.68 + 4.*3.98)*3.55*1.010 = 148.12
calories in Walter's beer. Note that 61.5% come from alcohol, and 38.5%
come from the residual extract.
Errors in the formula for calories using A and RE will be under 1%. Errors
in Balling's approximations can be as large as 3-5%.
I am looking forward to Milwaukee for I know there will be a big HBD turnout
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